1988 3.7 MerCruiser Motor will only run WOT

[ecase1988]

I apologize if someone has already answered/solved this issue somewhere else but i didnt see another thread with a issue that matches my problem.

The boat ran good a month ago when i took it fishing and now it will not stay running. My Mercruiser will only run if i have it throttled up, i used to be able to start it and let it run at higher idle for a minute or two then i could lower it down to idle speeds. Now it just dies when i pull the throttle back. I found some crud in the small fuel line that leads from the fuel pump to the carb, i removed the fuel line and brass elbow and cleaned both out. I then put them back on and the engine started again but the issue was still there( i didnt hold out much hope that cleanning it would actually fix the issue).

Any ideas? What other info would help you help me track down the issue?

 

[harringtondav]

Once you mentioned 'crud' all I can think of is 'crud'. The idle circuit in a carb uses very small passages to bleed fuel into the carb bores below the throttle plate. It doesn't take much to block them. Higher throttle positions deliver gas thru the venturi jets which are much larger. This could explain why you're ok at higher throttle positions. I'd recommend cleaning/rebuilding your carb AFTER you trace your fuel system back to the filter at a minimum, and find the source of the contaminants. .

 

[Bondo]

I apologize if someone has already answered/solved this issue somewhere else but i didnt see another thread with a issue that matches my problem.

The boat ran good a month ago when i took it fishing and now it will not stay running. My Mercruiser will only run if i have it throttled up, i used to be able to start it and let it run at higher idle for a minute or two then i could lower it down to idle speeds. Now it just dies when i pull the throttle back. I found some crud in the small fuel line that leads from the fuel pump to the carb, i removed the fuel line and brass elbow and cleaned both out. I then put them back on and the engine started again but the issue was still there( i didnt hold out much hope that cleanning it would actually fix the issue).

Any ideas? What other info would help you help me track down the issue?

Ayuh,...... Welcome Aboard,...... Besides bein' a Merc,...... Whatcha workin' on,..??..??

Was this little hose, yellow translucent tubin',..??
If so, that's just the fuel pump vent,.....
So long as there's no gas in it, it's ok,......

My guess is, yer fuel filter's fulla crap, 'n some of that crap has made it to the carb, pluggin' up the idle circuits, 'n probably more, that will become apparent in due time,....

I'd test my theory by pullin', 'n changin' the fuel filter, 'n examinin' the Contents, for anything but clean fresh gasoline,.....
After that, My next guess is, yer gonna be rebuildin' the carb,.....

 

[ecase1988]

Once you mentioned 'crud' all I can think of is 'crud'. The idle circuit in a carb uses very small passages to bleed fuel into the carb bores below the throttle plate. It doesn't take much to block them. Higher throttle positions deliver gas thru the venturi jets which are much larger. This could explain why you're ok at higher throttle positions. I'd recommend cleaning/rebuilding your carb AFTER you trace your fuel system back to the filter at a minimum, and find the source of the contaminants. .

Ok, thanks for the info i will start with this

Ayuh,...... Welcome Aboard,...... Besides bein' a Merc,...... Whatcha workin' on,..??..??

Was this little hose, yellow translucent tubin',..??
If so, that's just the fuel pump vent,.....
So long as there's no gas in it, it's ok,......

My guess is, yer fuel filter's fulla crap, 'n some of that crap has made it to the carb, pluggin' up the idle circuits, 'n probably more, that will become apparent in due time,....

I'd test my theory by pullin', 'n changin' the fuel filter, 'n examinin' the Contents, for anything but clean fresh gasoline,.....
After that, My next guess is, yer gonna be rebuildin' the carb,.....

Its a 1988 IMP Ashanti BowRider with a 3.7 MerCruiser in it. That i bought about a year ago.
Yes the hose was yellow translucent, ok there was no gas in it but it did have some black gunk in there. which i cleanned out

Any idea on where the fuel filter is located? I traced the bigger hose supply?(about 1/2inch) from the pump leading to the fuel tank but i do not see a fuel filter. I have a small access point directly over the fuel tank (about 1 foot by 1 foot) .

 

[harringtondav]

Guessing here, but I believe that vintage fuel pump has an integral strainer bowl and strainer screen above it. If so the bowl is unfastened, drops off the bottom of the pump, and the screen and gasket are above. Someone out here knows the p/n's by memory, but you can check it out while your waiting for better info.

Edit: Just checked my favorite competitive online parts catalogue. Your filter is located as I stated. Double check for your self, but I believe Sierra 18-7784 will work and is probably avail. here at iBoats. Else Merc. 35-8M0046752 is OEM, and just a couple $$ more expensive. <$10. The shipping may be more painful.

 

[Bondo]

Any idea on where the fuel filter is located?

Ayuh,..... I'm sorry, I saw the 3.7l in the title after I posted,......

As noted, you've got the pump mounted strainer,.....

You should buy a housin', 'n canister filter to mount just before the fuel pump, as they also knock the water outa the fuel, where yer strainer don't,.....